Anti-Pirin antibodies are used in the immunodetection of the protein encoded by the PIR gene. In humans, the canonical protein has a reported length of 290 amino acid residues and a mass of 32.1 kDa. Its subcellular localization is in the nucleus and cytoplasm. It is reported to be highly expressed in a subset of melanomas. A member of the Pirin protein family, it is a reported transcriptional coregulator of NF-kappa-B which facilitates binding of NF-kappa-B proteins to target kappa-B genes in a redox-state-dependent manner. Other names for this target antigen include probable quercetin 2,3-dioxygenase PIR, probable quercetinase, and pirin (iron-binding nuclear protein).